1. Field of the Invention
This invention relates to chemistry and, in particular, to novel bis-pyrazolone oxonol compounds useful as antihalation dyes in photographic products and processes.
2. Description of the Prior Art
Photographic light-sensitive elements are often provided with antihalation layers for the purpose of absorbing harmful reflected, scattered and/or diffused light which can adversely effect the quality of image reproduction. Such layers typically contain organic dyes possessing the desired spectral absorption properties distributed at a convenient coverage in a suitable polymeric hydrophilic colloid matrix. Since these dyes often have a deleterious effect on the light-sensitive layers used in the photosensitive element, it is important that these dyes be immobile and do not diffuse to the adjacent layers. Further, it is also generally necessary, particularly in films adapted for image reproduction by projection, that these dyes be rapidly and completely discharged or decolored (bleached) during the photographic processing steps to enable unhindered viewing of the developed image.
Although several pyrazolone dyes and, particularly bis-pyrazolone oxonol dyes, have previously been proposed as antihalation dyes in photographic products and processes (see, for example, U.S. Pat. Nos. 2,621,125; 3,502,474; and 3,795,519), none have satisfactorily met all of the desired requirements; in particular, they either bleach too slowly and/or are mobile in gelatin matrices.
A class of bis-pyrazolone oxonol dyes has now been found which does not possess the above-mentioned deficiencies of the prior art and which dyes are particularly suited as antihalation dyes in photographic products and processes.